Vacuum pump



Jan. 7, 1941. c F COLEMAN 2,227,441

VACUUM PUMP Original Filed Aug. 7, 1934 2 Sheets-Sheet l Ilium $7 7? 7676 @Hmwwng Jan. 7, 1941. c. F. COLEMAN 2,227,441

VACUUM PUMP Original Filed Aug. '7, 1934 2 Sheets-Sheet 2 d Clji'aolemaru,

VFW MW Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE VACUUM PUMP ofPennsylvania Application August 7, 1934, Serial No. 738,863 RenewedMarch 21, 1939 17 Claims.

My invention relates to improvements in mechanical gas pumps having arotating piston and utilizing a liquid as a sealing medium, andparticularly to the type used either as compressors or as high vacuumpumps and disclosed in U. S. Letters Patent No. 1,899,904, granted to O.S. Sleeper and C. J. Westin on February 28, 1933. An improved form ofthis pump is also disclosed in the application of Charles J. WestinSerial No. 724,- 9'74, filed May 10, 1934, now Patent No. 2,070,151,issued February 9, 1937.

One object of my invention is to provide new and improved means in a.vacuum pumping system for clarifying or cleaning the sealing medium offoreign matter, such as dirt, coming over into the pump with the gases.

Another object is to dehydrate or separate out any vapors or moisturesuch as water which may be mixed or dispersed in the sealing medium.

Another object is to extract any solvent which may have gone intosolution with the sealing medium.

lit is also an object of my invention to provide means for taking thedischarged sealing medium from the outlet compartment and passing thisthrough the purifying and dehydrating means or solvent stripping meanswithout having any of the vapors and gases coming over into this means.

A more specific object is to devise means whereby the purification anddehydration or solvent stripping of the sealing medium is made acontinuous automatic process.

lln; one modification of my invention clarifying means is associatedwith and made a part of the pump by a novel arrangement of passages andvalves 50 that the process is made continuous and automatic throughout.

In another modification of my invention solvent stripping means isembodied in the system in place of the clariiler.

In a third modification of my invention both a clarifier and a stripperare employed for completely purifying the sealing medium.

By means of these and other improvements which produce a continuallycleaned sealing medium, tree from moisture or solvents as will beunderstood from the specification, I obtain several benefits, such as:Higher vacuum, a more constant vacuum, the elimination of excessive Wearof the moving parts, and a greatly increased life for the sealingmedium.

In order to operate at practical efliciency, all moving parts must bemachined to close fits or small clearance so that they will cooperatethroughout the cycle with the lubricating and sealing medium, hereaftermerely referred to as oil, in forming a perfect or nearly perfect sealbetween the low and high pressure side of the pump.

The construction of this type of pump is such that an ample supply ofoil is continually circulating through the system. Dust and dirt,however, are drawn over with the gases into the pump and mixed with theoil so that through the continual recirculation of the oil it graduallybecomes more and more polluted, thereby lowering the efliciency of thepump and causing excessive wear on the parts. Where a lot of dirt comesover, which often is the case, the oil must be changed frequently. Thiscauses delays in operation and is also an item of considerable expenseon account of the large amount of oil used.

Another problem seriously afiecting the emciency of the pump is themoisture that usually is present in the gases. This moisture will bedispersed in the oil of the system and is discharged with the oil andgases into the oil reservoir un-- less otherwise directed. in order toobtain a high vacuum it is necessary to remove all the moisture from theoil before it is recirculated through the pump. Although provision ismade in the oil reservoir to have the larger drops of water settle out,this process is too slow on finely dispersed water, and a certainpercentage of moisture will he carried into the system with the oil andthus aggravate the difliculty.

I might mention here, by way of explanation, the very serious effect asmall drop of water will have on the vacuum it carried into the highvacuum side of the pump. For example, at a vacuum of 29", water vapor isformed at 80 F. and has a volume of 634 cubic feet per pound; at 29%."vacuum, water vapor is formed at F. and the volume is 2420 cubic feetper pound. it oil having water particles dispersed in it enters the highvacuum side, this water will vaporize at once and will very considerablylower the volumetric e ciency of the pump. This water vapor is againcondensed on the pressure side and discharged with the oil into theoutlet compartment.

The above difficulty is overcome by passing the oil as it comes from theoutlet compartment through an oil clarifier where the dirt and water orother volatile material of different specific gravity than oil isremoved and expelled from the system before the oil is returned to theoil reservoir for recirculation.

I have described above the detrimental efiect of moisture and othervolatile material it found as a finely divided suspension in the oiloras an emulsion Such mixtures can be separated by means of a clariflerdue to their difi'erence in specific gravity.

Some other volatile materials such as alcohol,

benzol, naphtha, acetone, carbon bisulphite and various other solventsactually go into solution in the oil, producing a mixture of uniformspeciflc gravity upon which the centrifugal separator or similarclarifier has no affect other than the removal of suspended mechanicalimpurities.

When operating a vacuum system containing this type of material, any airwhich is originally in the system, and such air as leaks in during theoperation, passes through the condenser and vacuum pump and comes outsaturated with solvent. The amount of solvent present depends on thetemperature of the air and the volatility of the solvent. Even with asecondary condenser in the line it is impossible to remove all thesolvents. Some of the solvent in passing through the pump is dissolvedin the oil. If this is not removed from the oil it will gradually thinthe oil to such an extent that the required operating vacuum cannot bemaintained.

To overcome this difllculty I take the oil from the outlet compartmentand pass it through a solvent stripper before it is returned to the oilreservoir.

By these means I obtain a very efliciently operating pump regardless ofthe impurities mixed or dissolved in the oil, as the oil is maintainedin a pure condition and therefore, may be used for a much longer timewithout the need for renewing it.

The principles of construction and novel arrangement of parts will bereadily understood by reference to the annexed specification anddrawings.

In the drawings:

Figure 1 is an end elevation, partly in section, illustrating onemodification in which a clarifier is associated with the pump;

Figure 2 is a view partly in section illustrating the details of thecheck valve employed in Figure Figure 2a is a plan view of the valvepoppet of Fig. 2;

Fig. 3 is a view of a pump with an attached solvent stripper, thestripper being shown in cross-section;

Figure 4 is a sectional view along line 4-4 of Fig. 3, and

Figure 5 is a fragmentary view illustrating an arrangement employingboth a clarifier and a stripper.

Referring to the drawings, there is shown a rotary pump having a housingI 0 mounted on a hollow base II. In the housing is formed 3." cylinderl2, closed at both ends by end-plates, and partially surrounded by ajacket l3, adapted to receive water or other cooling medium, and havinga passage ll furnishing communicating means with the hollow base I I forthe escaping gases. The housing In is extended at the top to form aninlet compartment ii of rectangular outline connected directly to andextending the full length of cylinder l2 and being closed at both endsby extension on the cylinder endplates. Provision is made at l6 for anintake connection to a chamber or space lGa to be evacuated. Alongsidethe intake compartment IS in the extension of housing I is formed theoutlet compartment II with suitable accommodations for the outlet valvel8 which may be of the general construction shown. The outletcompartment is connected on the one side to I the interior of thecylinder 12 by a row of cylindrical discharge ports l8, and closed onthe other or outer side by a cover-plate 20 which is made hollow so asto provide a free passage 2| for the discharged gases into thecorresponding passage H of the housing to which it is connected. Theinside wall 22 of the passage 2| in cover-plate 20 is made with aprojection 22a extending in over valve ll so that it will prevent theoil from following the gases on their way down into the base. Anotherbaflle "a is secured to the pump wall and is arranged to cause the gasesto pass in a tortuous path from the outlet valve to the passage 2|. Thepassage taken by the oil into the reservoir ll of the base II will bedescribed later.

Through the center of cylinder I2 is mounted a shaft 23 with supportinghearings in the cylinder end-plates and driven from any suitable sourceof power. Keyed or otherwise fastened to shaft 23 is the rotaryeccentric 24 which carries on the outer surface the tube-shapedoscillating piston 25. A slide valve 26 is fastened to the piston 25 bymeans of a hinge 21 of such construction as to provide a gas-tight,although flexible connection, and through this connection valve 26receives a reciprocating rectilineal motion in the rectangular inletcompartment l5, and as the valve 26 slides back and forth the inletports 28 connect the inlet compartment I5 with the cylinder l2 at theproper time of the cycle.

The oil drains off through an opening 80, placed at a suitable height inthe wall of the outlet compartment so as to retain within thecompartment a sufficient amount of oil for completely covering theoutlet valve [8, only the excess oil running out through the connectingpipe line into the oil clarifler 99.

The oil clarifler may be any suitable emulsion separator, such as the DeLa Val centrifugal separator, placed at such a level that the oil willrun by gravity from compartment l1 into the receiving funnel 97 ofclarifier 99. The clarifier 99 may be an entirely separate unit, mountedaside from the pump and driven from a source of power separate from thatdriving the pump. I prefer, however, to mount the clarifier 98 on anextension il b of the base II and drive it as an attachment of the pumpdirect from the pump shaft 23 by means of any suitable transmission suchas gearing or belting 99a. By so doing it is at all times properlysynchronized with the pump and is automatically started and stopped withthe pump.

While it is quite possible to lift or force the oil from compartment I!to a higher level by means of the pressure created at each discharge,such arrangement would establish an undesirable back pressure and Ihave, therefore, only shown the gravity draining system.

This system consists in general of a novel arrangement of pipeconnections which forms a trap, preventing the escape of any gasesthrough this passage and still permits free draining of the oil. It alsoincludes, in combination with the trap, the novel construction.

and positioning of a check-valve to prevent the oil from rushing overtoo fast when pressure is created on it or a head is built up withincompartment I1, and to prevent emptying. of the trap by sudden rushes ofthe exhaust gases. Considerable pressure is created on the oil incompartment I! at each discharge of the pump and this would force somuch oil out that the valve I8 would be left bare and unsealed unlessthe current of oil in the line is temporarily retarded while thepressure is relieved through the escape of the gases. Particularly isthis the case when starting the pump or when operating at a low vacuum.

The preferred construction and arrangement of parts may be described asfollows: An outlet pipe 8I is'connected at one end to the opening in thewall of compartment I1 and has a T 82 at the other end. The loweropening of 82 is connected to the vertical pipe 83, which forms one legof the trap. The bottom of the trap is formed by the horizontal pipe 85connected through elbows 84 and 86 to 83 on the one side and to thevertical check valve 81 on the other side. The check valve 81 togetherwith the pipe 88 fastened to its top constitutes the other vertical legof the trap. It should be noticed that pipe 88, which is connected byelbow 89 to the horizontal over-flow pipe 90, is of such length thatpipe 90 is at a slightly lower level than intake pipe BI, thusestablishing a gravity drain for the oil. At the far end, pipe 90terminates in a T M, which has at its lower end the vertical pipeconnection 92 leading down through cover 96 into the clarifier funnel91.

At the top of the two T's 82 and 9| is connected, by means of reducerelbows 93 and 95, a vent pipe-line 94 which serves the purpose ofequalizing the pressures in lines 81 and 88 and prevents any possibilityof the oil hanging up in line 83 after the check valve 81 has beenmomentarily closed by the discharge pressure in com partment I1. Openvents at the top of the Ts 82 and BI might be used but at such times asthe pressure is applied to the oil in leg 83, closing the check valve81, some oil would be forced out of the vent and squirt all over themachine which, of course, is objectionable and is entirely eliminated bythe connection 94. It may also be stated that this connection is of avery small size so that only small quantities can pass over this way.Normally no oil will pass through pipe 94 although some gases might, buton account of the small size of the pipe, the amount of gases passing isso small as to be unnoticeable.

As described, the oil enters the clarifler through pipe 92, passesthrough the centrifuge or other dehydrating and purifying means, and thedirty water is separated out and discharged through nozzle 91, while theclean oil passes through nozzle 98 into the funnel I00 and thence intothe oil reservoir ll. The funnel I00 is connected through check valveIOI, elbow I03 and pipe I02 with reservoir ll of the base II. The checkvalve Illl is normally open so that the oil can pass freely by gravityinto the base, the funnel being placed at such a level that it is abovethe oil level maintained in reservoir 4|. At times when there is a largedischarge of gases from the pump, sufiicient pressure is momen-- tarilycreated on the oil in reservoir II to force oil out and spill over thetop of funnel I00. This is prevented by the novel construction andpositioning of check valve I0 I.

Both valves, 81 and IIII, are identical in construction, and when placedin the relative position shown in Fig. 2, operate in the same manner andproduce the same results. Fig. 2 may therefore, represent either one.When first examining Fig. 2, the valve shown will appear to be ofexactly the same construction as most of the common check-valves of thistype, but there is a decided difference as will be explained below.

The common check valves are normally closed, and are opened and keptopen by the pressure of the current flowing through the line. The momentthe pressure discontinues, the valve closes so that nothing can flowthrough either way. In my construction the valves 81 and IN are normallyheld open by gravity, permitting the slow moving current of oil to passfreely by gravity through it in either direction, and they can only beclosed by a rapid building up of pressure on the oil in compartments I1or II, which pressure would create a rush of oil of sumcient volume tolift the poppet in the valve and thus close the valve. It will benoticed that the gravity flow of oil from outlet compartment I11 throughlines 8I--92 is in the direction of the arrows and the momentarypressure referred to above builds up a rush of oil in the same directionas the gravity flow. In the line 12, con necting funnel I80 withreservoir M, the flow of oil by gravity is normally in the direction ofthe arrows but the momentary pressure creates a rush of oil in thereverse direction and in this case therefore, produces a back current.From this it will be understood that the valves ti and IM are located intheir lines with respect to the direction of the anticipated momentarycurrentrush without any consideration being given to the normal gravity,flow. The valves are, therefore, placed in their respective lines sothat an increase in the flow of oil or a current-rush against the valvepoppet I05a will lift this against the seat I04?) and close the valvemomentarily.

Ordinarily the valve poppet is made from bronze or iron but I sometimesfind it desirable to make this part of a lighter material such asaluminum or dow-metal in order to make the valve more sensitive andresponsive to less pronounced increases in current flow.

The valve consists of the customary two piece housings IM and I01 withsuitable provisions at both ends for connection to the pipe lines. Ahearing I06; supported by a cross-rib I06a in the lower part I01 of thehousing, is provided as a central guide and support for the stem I05 ofthe valve-poppet. The rib I061; is of such narrow outline so that amplespaces Illla are al lowed on both sides for the free passage of liquidin either direction. An upper guide IMa is formed in the diaphragm ofthe upper housingpart IM for the poppet head I051). The lower part ofguide IIMa is shaped into a. suitable valve seat I04b which willcooperate with the shoulder Ill5a of the poppet to shut the passage ifand when the poppet is lifted and pressed against this seat. Normallypoppet-shoulder I050, rests on top of guide I06 and the shoulder I05a isof such size that it extends out over the guide I06 into the path of anycurrent-rush set up in the line from below. The head I051) is serratedor grooved on the side as indicated in Fig. 2a so that any liquid canflow freely through the guide IIMa. when the valve is open or in theposition shown in Fig. 2.

When it is desired to remove the volatile solvents a stripper III, Figs.3 and 4, is used in place of clarifier 99. The stripper may consist of asimple trough with electric heaters I20 clamped to the bottom I2I, sothat the oil coming through the inlet H4 and flowing over the hot bottomI2I will be heated sufficiently to boil off the solvent, the solventvapors being allowed to escape to the atmosphere. To make the solventstripper more effective and obtain greater emciency from the electricheaters, I prefer to make it enclosed, as shown in Figs. 3 and 4, andwith a bottom of sufilcient area so that the oil will spread out in athin layer over the heated surface. In order to retain the heat withinthe boiling chamber, the sides and top may be covered with someinsulating material II8, held in place by some form of a guard H9. Theheater compartment may also be enclosed if desired.

While I have shown the boiling chamber of rectangular cross section,Fig. 4, this might be circular or of any other convenient outlineproviding suificient heating surface and ample head room for the vaporsto pass oif. In the embodiment of my invention, chosen to illustrate theprinciples of construction, I have shown two electric heaters Ifastened-to the bottom I2I, but in some cases one heater may besuflicient, 20 and then again it more heat is desired, as for example ifit is desired to boil 011' any water dispersed in the oil, which wouldrequire more heat on account of the higher boiling point, provisionmight be made for several more heaters and some additional heaters mayalso be clamped to the sides. The heaters may be connected at I26 to theline of current supply. This line may be connected to the switchcontrolling the prime mover of the pump so that when the pump is startedthe current supply for the heaters is also connected. Heat controllingmeans such as thermostats may be provided in this line so as to maintaina uniform and constant temperature in the stripper. Other means ofheating may be used such as gas or steam. If steam heating is preferredthe boiling chamber may be completely or partly enclosed in a steamjacket or a steam coil placed on the bottom of the chamber. The inlet II4, is in this case made large enough to serve as inlet for the oil andoutlet for the vapors, but separate oil inlet and vapor outlets may beprovided.

The oil is drawn off from the pump outlet c0mpartment I I through thedrain 8!, trap 8385, check valve 81 and connections II2I I3 into thestripper III. Here the solvents and also the moisture, if so desired,are boiled off, passing out through the duct II3-I II while the purifiedoil drains into the funnel I90 through the connections I22--I24. A trapI25 is provided on the end of line I24 so that no vapors can pass outthrough this line. From the funnel I00 this oil passes into thereservoir 4| as described in connection with the clarifier. The funnelI90 may not be necessary but this provides space for the simple trap I25(any form of trap may be used), and also makes it more convenient tochange from a system using the clarifier 99 into a system using thestripper III. The drain line and trap 8I81 with pressure equalizer 94operates the same here as was described in connection with theclarifier, the only difierence being in providing the vapor outlet I I5-I I1, which may be connected to the outside of the building or, if itis de- 5 sired to reclaim the solvents, to the secondary condenser. Aseparate condenser and receiver may, of course, be used.

The heat in the oil that has passed through the stripper III, is readilytaken care of by radi- 70 ation in the reservoir M and the coolingsystem 53 provided here. The temperature of the stripped oil is only afew degrees higher than the normal operating temperature of the oil.

Actual operating tests with alcohol vapors 75 passing through the pumpand allowed to dilute the oil show that the vacuum is decreased to aslow as 22" while by the eflicient automatic removal of the solvents andpurifying oi the oil through the use of the stripper, the pump willoperate and maintain a vacuum within a fraction 5 of a millimeter.

When the sealing medium contains both types of impurities, both theclarifier and the stripper may be used at the same time. In Fig. 5 Ihave shown a fragmentary view of connections 101' 10 using both kinds ofpurifiers, the arrangement being like that of Fig. l with a stripper IIIinserted in the pipe 92 leading to the clarifler 99, the inlet being at92a, and the outlet at 92b. A vent pipe III is provided as in Fig. 3, tocarry 15 01f the vaporized solvents. Such an arrangement frees the oilof both solvents and foreign matter. .It will be understood that thestripper III could be inserted between the clarifier 99 and the funnelI00 instead of in the position 20 shown.

It is desirable to have all the oil, except as needed for sealing, drainout of compartment II through opening 80 and thus pass through theclarifier 99 or stripper III so that only pure oil 25 returns into thereservoir M for recirculation. The arrangement of and construction ofthe valve assembly I8 in cooperation with the deflector plates I'Ia,22a, and 22b within compartment I1, is such that the liquid matter, oiland water, en- 30 tering is prevented from passing over with the gasesand vapors into passages 2I and I4.

Outlet compartment I1 is of such area that ample space is provided forsufficiently large passages between the several deflector plates within35 it to permit the compressed gases, discharged through ports I9, toexpand the moment they enter this compartment in order to lower thepressure and incidentally the speed at which the gases and vapors flowout of the compartment 40 into passages 2I and I4 on their way to thedegaser and devaporizer 42 in the base II.

The gases and vapors come down through passages 2I and I4 into the baseII and thence through a degaser and devaporizer and out of 45 the pumpat Hz: into the atmosphere or into a secondary condenser. The oil on theother hand returns purified and dehydrated from the clarifier 99 or thestripper II I through connection I02 into the reservoir 4| of the baseII. This is of 50 such construction as to provide ample space for thestoring of the oil in reservoir H and also provides head-room or airspace above the oil level for the gases to pass out of the system.Connections are made from the reservoir 4| at 50, through pipe line 5Ior other means at a suitable point in the reservoir, so that the cleanoil is forced into the pump system and ejected at suitable points suchas 52, 52a and 23a for lubricating and sealing purposes. 00

From the above description it can readily be understood that through myinvention a very efficient system of automatically purifying the oil isobtained regardless of the amount of water and dirt or solvents that maycome over into the 65 pump. A small amount of water in the form of watervapors may come over and be condensed outin the devaporizer. This waterwill settle down at the lowest point in the reservoir 4| and from herebe drawn off at 50 together with the oil. I have found, however, thatthis is not constant but rather periodic and the amount of watersettling out is so small that it does not have any appreciable effect onthe efliciency oi the pump, because it is not allowed to accumulate butis instantly removed by the rapid recirculation ol. the oil.

It will be understood that the vacuum pump as disclosed herein isemployed as a component 5 part of a vacuum system, several differentforms of which are known in the art, such as vacuum drying systems,vacuum impregnating systems, and vacuum processing systems. All suchsystems involve a vacuous chamber or space to which the vacuum pump isconnected and from which the pump draws gases which may be ladened withdirt, dust particles, moisture and other vapors as hereinaboveindicated.

I have herein described the principle of my invention and illustratedthree embodiments thereof. Various modifications will occur to thoseskilled in the art, and I desire it to be understood that allmodifications which fall within the terms of the appended claims are tobe considcred as falling within the scope of my invention. The termpurifier as used in the appended claims is to be interpreted broadly tocover either a separator or a stripper.

"What I claim is: i. In combination, a vacuum pump having a dischargevalve chamber, an oil reservoir therefor, an oil purifier for removingliquid impurities from oil, means for pumping oil through the pump intothe discharge valve chamber of the 3d pump, a pipe connection from thevalve chamber for passing the discharged oil into said purifier, saidconnection including a trap to prevent gases from entering saidpurifier, and means for returning oil from the purifier to thereservoir.

35 2. In combination, a pump having a discharge valve chamber, an oilreservoir therefor, means for-pumping oil through the pump into thedischarge valve chamber of the pump, an oil puriher, a pipe connectionfor passing the discharged so oil from the valve chamber to saidpurifier including a trap to prevent the passage or gases, and acheck-valve in said connection normally biased open to permit a steadycontinuous flow oi oil to the purifier but being operable upon -15increased flow in the same direction to close said connection andthereby prevent the emptying of said trap.

3. In combination, a pump having a discharge valve chamber, an oilreservoir therefor, means so for pumping oil through said pump into thedischarge valve chamber of the pump, an oil puriher, a pipe connectionfor gravity draining oil from the valve chamber to said purifierincluding a U-shaped trap to prevent the passage of 55 gases, a bleederpipe connecting the upper ends of the legs of the trap to equalize thepressure therein, and a check-valve in said connection normally biasedopen to permit a steady continuous flow of oil to the purifier and beingoperable 60 upon increased flow in the same direction to close saidconnection and thereby prevent the emptying of said trap.

i. In combination, a pump having a hollow base and an exhaust valvechamber, an oil reser- (25 voir in said base, means for circulating oilthrough said pump into the exhaust valve chamber thereof, means forpassing the exhaust gases from the exhaust chamber through the hollowbase, an oil purifier, a pipe connection for passing the discharged oilfrom the valve chamber to said purifier including a trap to prevent thepassage of gases, a check valve in said connection normally biased opento permit a steady continuous flow oi oil to the purifier and beingoperable upon '15 increased flow in the same direction to close saidconnection, and a connection for returning the purified oil from saidpurifier to said reservoir including a check valve to prevent back-nowIrom said reservoir.

5. In combination, a pump having a hollow 6 base and an exhaust chamber,an oil reservoir in said base, means for passing the exhaust gases fromthe exhaust chamber through the hollow base, a separator arranged withinsaid hollow base in the path or said gases, an oil purifier, 10 a pipeconnection for gravity draining oil from the valve chamber to saidpurifier including a U- shaped trap to prevent the passage of gases, ableeder pipe connecting the upper ends of the legs or the trap toequalize the pressures therein, 15 a check valve in said connectionnormally biased open to permit the steady continuous flow of oil to thepurifier and being operable upon increased flow in the same direction toclose said connection, and means ior returning the purified oil 20 fromsaid purifier to said reservoir, including a check valve to preventback-flow from said reservoir.

6. In combination, a vacuum pump having a discharge valve chamber, anoil reservoir there-- all for, a solvent stripper tor stripping liquidsolvents from oil, means i'or pumping oil through the pump into thedischarge valve chamber of the pump. means in the discharge valvechamber for separating the oil from the discharge gases, and pipeconnections for returning the separated oil from the valve chamberthrough said stripper back to said reservoir.

7. In combination, a vacuum pump having a discharge valve chamber, anoil reservoir therefor, a centrifugal separator for separating solid andliquid impurities from oil, means for pumping oil through the pump intothe discharge valve chamber of the pump, means in said valve chamber forseparating the oil from the discharge 40 gases, and pipe connections forreturning said separated oil from said valve chamber through saidcentrifugal separator and back to said reservoir.

8. In combination, a vacuum pump having a discharge valve chamber, anoil reservoir therefor,

a centrifugal separator for separating solid and liquid impurities fromoil, a solvent stripper for stripping liquid solvents from oil, meansfor pumping oil through the pump into the discharge valve chamber of thepump, means in said valve chamber for separating the oil from thedischarge gases, and pipe connections for returning said separated oilfrom said valve chamber through said centrifugal separator, through saidstripper and back to said reservoir.

9. The herein described art which includes the steps of continuouslywithdrawing moisture and particles from a space to be evacuated, forcingthe moisture and particles into an oil sealed space wherein the oilmoisture and particles are mixed into a sludge, immediately separatingthe sludge into its component parts, immediately returning the oil tosaidoil sealed space, and discharging the moisture and particles. 5

10. The combination with apparatus having a vacuous chamber from whichsolids, moisture and gases are drawn off during evacuation thereof, ofevacuating means utilizing a sealing lubricant, means connected to saidevacuating means for supplying sealing lubricant to said evacuatingmeans, said evacuating means being constructed so that the solids andliquids taken therein are mixed with said lubricant to form a sludge,separating means adapted to separate the lubricant from the solids andliquids, means for conveying said sludge from said evacuating means tosaid separating means, and means for returning said lubricant from saidseparating means to said second mentioned means.

11. The combination with apparatus having a vacuous chamber from whichsolids, moisture and gases are drawn of! during evacuation thereof, of arotary pump utilizing a sealing lubricant, means connected to said pumpfor supplying sealing lubricant thereto, said pump being constructed sothat the sealing lubricant runs through the interior thereof and mixeswith the solids and liquids drawn therein to form a sludge, separatingmeans adapted to separate the lubricant from the solids and liquids,means for conveying said sludge from said pump to said separating means,and means for returning said lubricant from said separating means tosaid first mentioned means.

12. The combination with apparatus having a vacuous chamber from whichsolids, moisture and gases are drawn on during evacuation thereof, ofevacuating means utilizing a sealing lubricant, means connected to saidevacuating means for supplying sealing lubricant to said evacuatingmeans, said evacuating means being constructed so that the solids andliquids taken therein are mixed with said lubricant to form a sludge, acentrifugal separator, means for conveying said sludge from saidevacuating means to said separator, and means for returning saidlubricant from said separator to said second mentioned means.

13. The combination with apparatus having a vacuous chamber from whichsolids, moisture and gases are drawn off during evacuation thereof, of arotary pump utilizing a sealing lubricant, means connected to said pumpfor supplying sealing lubricant thereto, said pump being constructed sothat the sealing lubricant runs through the interior thereof and mixeswith the solids and liquids drawn therein to form a sludge, acentrifugal separator, means for conveying said sludge from said pump tosaid separator, and means for returning said lubricant from saidseparator to said first mentioned means.

14. The combination with apparatus having a vacuous chamber from whichsolids, moisture and gases are drawn off during evacuation thereof, ofevacuating means utilizing a sealing lubricant, a storage tank connectedto said evacuating means for supplying sealing lubricant to saidevacuating means, said evacuating means being constructed so that thesolids. and liquids taken therein are mixed with said lubricant to forma sludge, separating means adapted to separate the lubricant from thesolids and liquids, means for conveying said sludge from said evacuatingmeans to said separating means, and means for returning said lubricantfrom said separating means to said storage tank.

15. The herein described art, which includes the steps of removing waterand other foreign matter from a space to be evacuated, transferring thewater and foreign matter to a chamber sealed by oil so that the waterand foreign matter are mixed with the oil, removing the resultantmixture from said oil-sealed chamber, immediately centrifuging themixture to separate the water and foreign matter from the oil before anysubstantial emulsion of the oil occurs, and returning the oil to saidoil-sealed chamber.

6. The combination with apparatus having a vacuous chamber from which acondensable vapor. is drawn ofi during evacuation thereof, a pump forevacuating said chamber, a source of lubricant for lubricating andsealing said pump, means for continuously supplying lubricant from saidsource through the interior of said pump and discharging the same at thedischarge port of said pump, said pump being operable to compress thevapor drawn from said chamber whereby a portion thereof is condensed andat least a part of the condensate is mixed with the lubricant and isdischarged from said pump in the form of an emulsion, separating meansadapted to separate the condensate from the lubricant, means forcontinuously conveying the emulsion from the discharge port of said pumpto said separating means, and means for returning the condensate-freelubricant from said separating means to said source of lubricant.

17. The combination with apparatus having a vacuous chamber from whichwater vapor is drawn off during evacuation thereof, a. pump forevacuating said chamber, a source of oil for lubricating and sealingsaid pump, means for continuously supplying lubricating oil from saidsource through the interior of said pump and discharging the same at thedischarge port of said pump, said pump being operable to compress thevapor drawn from said chamber whereby a portion thereof is condensed anda part of the condensate is mixed with the oil discharged from said pumpto form an emulsion, a centrifugal separator, means for continuouslyconveying the emulsion discharged from said pump to said centrifugalseparator, and means for returning the condensate-free oil from saidseparator to said oil source.

CHARLES F. COLEMAN.

